The purpose of this research is to develop an empirical basis for an impulse noise Damage Risk Criteria. The strategy behind the research is to determine the relation between the parameters of the impulse and the concomitant changes in hearing and cochlear histology. A modified shock tube facility, the exploding wire phenomena, and the spark discharge are to be used to systematically generate a variety of impulse noise environments. The chinchilla will be used as the experimental animal with indices of hearing function to be: Auditory Evoked Response threshold, behavioral quiet threshold, temporal summation function, difference limens for frequency and intensity, and the reflex temporal integration thresholds. The cochlea of the exposed animals will be histologically examined using the surface preparation and ultra-thin sectioning techniques. The parametric study of impulse noise will be followed by low-level, long-term exposures and will more closely model realistic noise environments. This data is a necessary prerequisite for the determination of what constitutes a potentially hazardous impulse noise environment and how to audiometrically evaluate the hazard, and will ultimately contribute to the establishment of a safe Damage Risk Criteria. BIBLIOGRAPHIC REFERENCES: Woodford, C. M.; Henderson, D.; Hamernik, R.P.; Feldman, A.: "Static Acoustic Impedance of the Chinchilla Middle Ear: Awake and Sedated"., J. Acous. Soc. Amer., 58: 1100 (1975). Eames, B. L.; Hamernik, R. P.: Henderson, D.: Feldman, A.: "The role of the Middle Ear in Acoustic Trauma From Impulses". Laryngoscope, LXXXV: 1582 (1975).